The present invention relates generally to a method for applying a layer of plastic material to a glass sheet and, in particular, to a method for producing an anti-lacerative window assembly for use in automotive vehicles.
It has been found that the addition of a plastic layer bonded to the inboard glass surface of a conventional laminated windshield can further increase the safety effectiveness of the windshield. This plastic layer has typically been termed an anti-laceration shield since it has been found that the additional plastic layer will appreciably reduce the number and severity of lacerative injuries to persons thrown against the windshield under all impact conditions. Further, it has been found that the anti-laceration shield, when produced under certain conditions of manufacture, improves the ability of the laminated windshield to decelerate movement of a person thrown against the windshield, while also increasing the penetration resistance of the windshield as compared to conventional laminated windshields. Also, the laceration shield reduces the amount of flying glass and thus the injury to car occupants as a result of objects that may be thrown against he windshield from overpasses or elsewhere outside the vehicle.
An example of one type of anti-lacerative windshield is disclosed in U.S. Pat. No. 4,242,403. In this patent, the laceration shield includes a penetration resisting multi-layer body consisting of an inner layer of relatively soft, extensible plastic material such as polyvinyl butyral, which is adhered to the inboard surface of the windshield, an intermediate layer of more durable plastic such as polyester, and an outer coating of an abrasion resistant material. Another type of anti-lacerative windshield is disclosed in U.S. Pat. No. 3,808,077 wherein a single layer of polyurethane is utilized as an anti-laceration shield.
While the effectiveness of a laminated windshield having an anti-laceration shield is obvious, very few vehicles utilize such a windshield. The chief reason for this limited use has been the difficulty experienced in trying to manufacture a windshield with an anti-laceration shield on a production basis. In the automotive industry, the standard for windshields is very high, especially as to optical qualities, and it has been very difficult to manufacture a windshield having an anti-laceration shield which is free of optical defects. Even when the individual sheets of the laminated assembly are free from optical defects before bonding them together, it is difficult to join them and preserve the optical qualities.